A Magmatic Trigger for the Paleocene Eocene Thermal Maximum?

Andrea Dubin, Ph.D., 2015Bernhard Peucker-Ehrenbrink, Advisor

Fifty-six million years ago Earth experienced rapid global warming, caused by the release of isotopically light carbon into the ocean-atmosphere system. I test the hypothesis that the Paleocene-Eocene Thermal Maximum (PETM) warming and isotope excursion were caused by the intrusion of magmatic sills into organic-rich sediments in the North Atlantic Magmatic Province (NAMP), which would cause heating and metamorphic reactions in a thermal aureole around the intrusion. If these sediments are rich in organic matter, large volumes of isotopically light carbon are rapidly released. I examine geochemical evidence from lead, osmium, and organic carbon to place constraints on the extent the carbon isotope excursion during the PETM may have been caused by this process. Potential analogs are examined to determine the behavior of these elements during thermal alteration. I find that lead is not a suitable proxy for carbon mobilization; however osmium is mobilized with carbon. The entire marine osmium isotope anomaly at the PETM could be explained without the need for enhanced continental weathering. Based on estimates of the extent of mobilization of organic carbon and osmium, 47% to 60% of the carbon released at the PETM may have been derived from thermal alteration of sediments in the NAMP.